Fast compiler: Load globals variables directly from property cells....

src/fast-codegen.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 196 matching lines @@
 
 
 void FastCodeGenSyntaxChecker::VisitSlot(Slot* expr) {
   UNREACHABLE();
 }
 
 
 void FastCodeGenSyntaxChecker::VisitVariableProxy(VariableProxy* expr) {
   // Only global variable references are supported.
   Variable* var = expr->var();
-  if (!var->is_global()) BAILOUT("Non-global variable");
+  if (!var->is_global() || var->is_this()) BAILOUT("Non-global variable");
+
+  // Check if the global variable is existing and non-deletable.
+  if (info()->has_global_object()) {
+    LookupResult lookup;
+    info()->global_object()->Lookup(*expr->name(), &lookup);
+    if (!lookup.IsValid() || !lookup.IsDontDelete()) {
+      BAILOUT("Non-existing or deletable global variable");
+    }
+  }
 }
 
 
 void FastCodeGenSyntaxChecker::VisitLiteral(Literal* expr) {
   BAILOUT("Literal");
 }
 
 
 void FastCodeGenSyntaxChecker::VisitRegExpLiteral(RegExpLiteral* expr) {
   BAILOUT("RegExpLiteral");
@@ skipping 250 matching lines @@
 }
 
 
 void FastCodeGenerator::VisitVariableProxy(VariableProxy* expr) {
   ASSERT(expr->var()->is_global() && !expr->var()->is_this());
   Comment cmnt(masm(), ";; Global");
   if (FLAG_print_ir) {
     SmartPointer<char> name = expr->name()->ToCString();
     PrintF("%d: t%d = Global(%s)\n", expr->num(), expr->num(), *name);
   }
-  EmitGlobalVariableLoad(expr->name());
+
+  // Check if we can compile a global variable load directly from the cell.
+  ASSERT(info()->has_global_object());
+  LookupResult lookup;
+  info()->global_object()->Lookup(*expr->name(), &lookup);
+  // We only support DontDelete properties for now.
+  ASSERT(lookup.isValid());
+  ASSERT(lookup.IsDontDelete());
+  Handle<Object> cell(info()->global_object()->GetPropertyCell(&lookup));
+  EmitGlobalVariableLoad(cell);
 }
 
 
 void FastCodeGenerator::VisitLiteral(Literal* expr) {
   UNREACHABLE();
 }
 
 
 void FastCodeGenerator::VisitRegExpLiteral(RegExpLiteral* expr) {
   UNREACHABLE();
@@ skipping 84 matching lines @@
 
 
 void FastCodeGenerator::VisitThisFunction(ThisFunction* expr) {
   UNREACHABLE();
 }
 
 #undef __
 
 
 } }  // namespace v8::internal